IF YOUR CALCULATIONS are correct, by the time you read this the United States will have successfully landed Sen. William L. Scott in the Khyber Pass. Delivery was scheduled for noon (local time) today, by U.S. embassy limousine following a first-stage approach by Air Force C141. And while it may not be quite the same as putting a man on the moon, we would argue that, with his latest voyage, the senator is making history, of a sort. For what we are witnessing is a another small step in what may well be the longest, permanent - not to say, giant - ripoff of the American taxpayer ever conducted by a first-term senator. In five years, the Virginia Republican has orbited an estimated 37 countries - without visible effect on the legislative process. And one thing his voyages do have in common with space travel is that the U.S. government pays the way.

We do not kid ourselves that there is any point in railing at the senator - a man who once convened a news conference to deny a description of him in New Times magazine as "the dumbest congressman of them all." He is, we judge, beyond the reach of reason and also, by all appearances, without shame. Reportedly, when asked by a State Department official why he had picked India, Pakistan and Afghanistan for his current trip (his third this year), his answer was simply that he had "never been there before." So much for legislative purposes. The best that can be said of Sen. Scott is that time is on our side (he has announced that he will not run for re-election next year) and that this trip promises to be relatively inexpensive (The Pentagon advises us that Sen. and Mrs. Scott are traveling on a space-available basis on scheduled flights of Air Force cargo planes).

The more interesting question is what Sen. Scott's grand tours say about the Senate's sense of shame. Congressional Quarterly, which does noble work trying to keep track of congressional travel, reports that 204 members of the House and Senate took at least 309 trips in 1976, which is about normal for an election year; in the previous year, 308 members took at least 544 foreign trips. This is not, then, a fertile field for shame. Moreover, it is probably fair to say that most congressional travelers can point to some reasonably serious and specific mission, duly authorized by a committee or at least a committee chairman, and at least loosely related to some legislative purpose.

But not in the case of Sen. Scott. When his committee chairman, Sen. James Eastland (D-Miss), was asked about the purpose of the current Scott trip, he replied: "Hell, I don't know. He told me, but I forgot." Pressed as to whether this might constitute an abuse of the senatorial right to travel at taxpayer expense, the chairman replied: "No more than any other trip." Now, we wouldn't want to hold that up as any more indicative of the general senatorial mood and manner than the performance of Sen. Scott. On the other hand, we aren't hearing any loud protests about it from Capitol Hill. At a time when the Congress is professing genuine concern about its standing with the public, and its appearances, this does make you wonder when - if ever - the congressional wanderlust will be included among those excesses that need to be subjected to more rigid standards of official conduct.